1. Field of Invention
This invention relates generally to apparatus for isolating an operating device against multi-dimensional vibration disturbances and, more particularly, to an apparatus for isolating sensitive instrumentalities on-board a space vehicle against on-board generated vibrational disturbances.
2. Discussion
It is becoming increasingly important in exploratory-type space missions to ensure the optimum performance of various instrumentalities aboard a space vehicle while operating in its orbital path and also at the time of launch. The reliability of performance of such instrumentalities as space telescopes may be interfered with due to the vibrational disturbances generated during the launching process as well as in flight by the on-board equipment, such as the attitude stabilizing reaction wheels. For example, in space vehicles whose mission it is to carry out telescopic surveillance, it is essential to maintain the mirrors focused on targets in space. Reaction wheels are known to generate vibrational frequencies over a range of 5 Hz to 100 Hz and greater, which could disturb the precise pointing of the telescope. Another example involves telescopic surveillance of x-ray radiation, which requires control of the vibration disturbances, otherwise the required x-ray images would be distorted and enlarged.
Protection of the sensitive instruments and devices on the spacecraft against the high G-forces and vibration during launch is accomplished by securing or releasably locking them in place during launch. Once the spacecraft is in orbit, the locked down instruments are deployed by being unlocked using pyrotechnic devices that ordinarily generate very high localized frequency vibrations.
It is generally known to use techniques for isolating vibration sensitive equipment against the adverse effects of vibration-generating disturbances. Such apparatus typically involves the use of elastomeric or rubber-like mountings which are interposed between the vibration-generating source and the affected operating equipment thereby absorbing the vibration thereby minimizing the transmissibility of the vibrational sources. The success of such basic rubber pads or cushions depends on the kinds of vibrational forces being generated. Effective isolation apparatus requires that it control the known kinds of multi-dimensional disturbances that result from rotating equipment such as, for example, the static imbalance, axial run-out as well as the moments generated due to dynamic imbalances that are applied in a lateral direction.
Rotating equipment generally will generate disturbances in five directions. When considered in the environment of an XYZ coordinate system, rotating equipment produces lateral forces in each of the X and Y direction, axial forces are in the Z direction, and the force moments due to dynamic imbalance are produced about the lateral X and Y axis.
The isolator devices of this invention can be employed to advantage in other apparatus where the functional requirement is the precise acquisition and maintenance of a target. For example, in a step and repeat lithographic process, the control of vibrational disturbances is essential. Wherever high-intensity pinpoint laser beams are employed to operate against a fixed objective, it is desirable to isolate the generated beam from any high frequency vibration and force moments. There is a need for isolator apparatus that can effectively, simultaneously respond to the diverse kinds of vibrational disturbances and moments, and thereby minimize the line of sight jitter interference with pointing, imaging and maintaining stability within the range of 0.4 .mu.rad to 0.64 .mu.rad.